1. Field
Embodiments of the invention relate to electronic systems, and more particularly, to bi-directional blocking voltage protection devices for integrated electronic systems.
2. Description of the Related Technology
Certain electronic systems can be exposed to a transient signal event, or an electrical signal of a relatively short duration having rapidly changing voltage and high power. Transient signal events can include, for example, electrostatic discharge (ESD) events arising from the abrupt release of charge from an object or person to an electronic system.
Transient signal events can damage integrated circuits (ICs) inside an electronic system due to overvoltage conditions and/or high levels of power dissipation over relatively small areas of the ICs. High power dissipation can increase IC temperature, and can lead to numerous problems, such as gate oxide punch-through, junction damage, metal damage, and surface charge accumulation. Moreover, transient signal events can induce latch-up (in other words, inadvertent creation of a low-impedance path), thereby disrupting the functioning of the IC and potentially causing permanent damage to the IC. Thus, there is a need to provide an IC with protection from such transient signal events.
FIG. 1 is a schematic block diagram of a conventional electronic system 1. The electronic system 1 includes a pin 2, an internal circuit 3, a resistor 4, a protection circuit 5, and a supply clamp 8. The internal circuit 3, the protection circuit 5, and the supply clamp 8 are each electrically coupled between a first supply voltage V1 and a second supply voltage V2, which can be power-low and power-high supplies, respectively. The resistor 4 is disposed in series between the pin 2 and the internal circuit 3, and the protection circuit 5 is electrically coupled between the pin 2 and the first supply voltage V1. The protection circuit 5 includes a first diode 6 and a second diode 7. The first diode 6 includes an anode electrically connected to the pin 2 and a cathode electrically connected to a cathode of the second diode 7. The second diode 7 further includes an anode electrically connected to the first supply voltage V1.
The protection circuit 5 can be used for protecting the pin 2 from a transient electrical event 9. However, the protection afforded by the protection circuit 5 can be limited for certain applications of the electronic system 1. For example, the protection circuit 5 may not be able to provide bi-directional protection to the pad 2 at low voltage levels, since it may not be feasible to configure the first and second diodes 6, 7 to have a relatively low breakdown voltage. Furthermore, even if the breakdown voltage of the first and second diodes 6, 7 can be reduced to a voltage level sufficient for the application, the first and second diodes 6, 7 can have a relatively large size and occupy a relatively large die area, which can affect production cost, capacitive loading on the pad 2, and/or signal integrity in high performance low noise applications.